1. Field of the Invention
The present invention relates to a control apparatus for a power conversion apparatus including a plurality of chopper circuits, and to a power conversion system including the control apparatus and the power conversion apparatus.
2. Description of Related Art
There is known a control apparatus for a boost converter as a power conversion apparatus, in which switching from off-state to on-state of switching elements of each of chopper circuits included in the boost converter is performed when a current flowing through a coil of each of the chopper circuits becomes 0. For example, refer to Japanese Patent Application Laid-open No. 2000-358368. In this control apparatus, the timing at which switching from off-state to on-state of the switching elements is performed is different from chopper circuit to chopper circuit, so that the switchings are performed at even time intervals for these chopper circuits. When the switching timings of the switching state of the switching elements are evenly spaced apart, a cycle period of increase and decrease of the current flowing through the coil is the same for ail the chopper circuits, and accordingly timings at which the currents peak in these chopper circuits respectively are evenly spaced apart. This makes it possible to reduce a ripple current in the boost converter.
However, to vary an output voltage or an output current of the boost converter, it is necessary to vary output currents of the chopper circuits. This requires to vary the timing of switching of the switching state at each of the chopper circuits. In this case, however, as shown in FIG. 23 which shows an example of variations with time of coil currents in a case where the control apparatus includes four chopper circuits, the timings at which the currents respectively flowing through the coils of the chopper circuits reach their peaks cannot be evenly spaced.